The invention relates to a contact for use in a zero insertion force socket. In particular, the terminals have non-symmetrical redundant beams which allow the terminals to compensate for mispositioned pins of a mating connector.
Zero insertion force sockets are known in the art. Generally, the socket has a base with terminals mounted therein and a cover which is slidably mounted on the base. Some type of cam means is provided to move the cover relative to the base.
The terminals provided in these prior art sockets are dimensioned to receive a mating pin therein. The pin is inserted into an open area of the terminal which requires a zero or minimal force for insertion. The cover with the pins mounted therein is then slid such that the pins move from the open area of the terminal to a restricted portion. In this restricted portion, the mating pins electrically engage arms of the terminals to provide the electrical connection therebetween. In one such socket, the portion of the terminal which mates with the mating pin has a first arm and a second arm extending from a connecting portion which connects the mating portion with a retention portion of the terminals herein. The first arm is significantly longer than the second arm. The first arm and second arm form a generally U-shaped cantilever member. The arms converge towards each other to form the restricted portion. When the mating pin is positioned in electrical engagement with the restricted portion, the first and second arms have different electrical resistance resulting in an unbalanced signal transfer between the arms. In addition, when the mating pins are improperly aligned in the socket, the mating portion is not adequately adjustable to adapt for the misposition of the pins. This is because the second contact arm is generally short and relatively rigid, thereby limiting its resiliency and preventing the second arm from adapting to the misaligned pin. In contrast, the lengthy first arm is resiliently deformable and can adjust to the misalignment of the pins. However, as the misaligned pin will not be held in electrical engagement with both the first and second arms of the terminal, an inconsistent electrical connection is provided.
U.S. Pat. No. 6,142,810 discloses a terminal wherein the electrical resistance between the pins and the terminals is a low. Each terminal has an engaging portion, a retention portion, a neck inter-connecting the engaging and retention portions, and a mounting pad. The engaging portion has a pair of cantilevers symmetrically arranged about a central line thereof and extending a predetermined distance from the neck in one direction and converging towards each other. The engaging portion rotates with respect to the neck such that the pair of cantilevers is reliably connected with a contact pin of the mating connector even when the pin is incorrectly positioned in the aperture. The retention portion has barbs for reliably retaining the terminal in the base. A mounting pad is positioned proximate to an extends perpendicular to the retention portion. While this terminal better compensates for mating pin misalignment, the close proximity of the mounting pad to the retention portion can result in an ineffective electrical connection between the terminals of the socket and the contact traces of a printed circuit board on which it is mounted. As warpage of the printed circuit boards is common, it is important to have terminals which have sufficient resiliency to compensate for the warpage. Additionally, as the socket and board have different coefficients of thermal expansion, the terminals must be able to compensate for relative movement to ensure that the solder connection between the mounting pads and traces is not rendered ineffective.
It would therefore be advantageous to provide a socket which has terminals which have sufficient resilient characteristics at both mating ends. In so doing misalignment in the mating components can be compensated and a positive electrical connection is affected.
The invention is directed to a terminal with use with a zero insertion force socket which electrically connects a mating connector to a printed circuit board or the like. The terminal has a pin engaging portion which has a pair of contact arms positioned to make electrical engagement with a mating pin. A retention portion extends from the pin engaging portion. Side edges of the retention portion are dimensioned to create a frictional interference with side wall of a cavity of the socket. A mounting portion extends from the retention portion in an opposite direction from the pin engaging portion. The mounting portion has at least one resilient leg which extends from the retention portion to a solder pad which is soldered to a substrate. The solder pad is spaced from the retention portion a sufficient distance to allow the at least one resilient leg to provide the resilient characteristics required to allow the at least one resilient leg to resiliently compensate for misalignment or movement of the solder relative to the solder pad.
In addition, the pin engaging portion has a pair of nonsymmetrical contact arms which are positioned to make electrical engagement with a mating pin. A first contact arm of the pair of contact arms is configured to have a longer electrical path across which signals are transmitted than a second contact arm. The first contact arm also has a reduced width compared to the second contact arm, such that the first contact arm is configured to have a matched inductance to the second contact arm.